Consider removing the @JsonCreator requirement

[lpandzic]

This feature would really simplify usage and provide convience for developers.
Considering everyday development techniques I've encountered regarding this issue the most basic use case boils down to:

class AClass {

  ... mandatory field m1, ..., mn
  ... optional field o1, ..., on

  AClass(m1, ..., mn) {
  }

  ... setters for o1, .., on

  ... other methods
}

One additional argument for tackling this issue are value types which will always be immutable.

[cowtowncoder]

I have an idea which would apply to jackson-databind, and might satisfy different requirements (convenience of detecting likely primary constructor; safety of not accidentally using a constructor that was not mean to be used). Given that without a no-arg constructor, @JsonCreator, or auto-detected single-argument (String, boolean, int/long, double) constructor there is no way to deserialize a value, I think it would be safe to auto-detect a multi-argument constructors if:

1. It is the only visible constructor class has
2. There are no @JsonCreator annotated factory methods
3. All arguments have either a name (implicit or explicit), or are injectable

Would this make sense?

/cc @christophercurrie

[lpandzic]

Would this make sense?

Yes.
I've made a pull request with tests for this issue.

[cowtowncoder]

Ok, one more related improvement:

FasterXML/jackson-databind#725

which I hope should actually further reduce the need for @JsonCreator. Fix is in master (for 2.6.0-SNAPSHOT). The basic rule is simple: if

1. There is no other visible creator and
2. All parameters have explicit or implicit name

a constructor will be used similar to if it was annotated. Cases that do not fall under this would be:

a. Multiple visible constructors: no attempt is made to know which one to use; no point guessing as there will always be some cases where determination impossible (same number of arguments, same visibility etc)
b. Single-argument case: due to ambiguity between delegating/properties-based variants this case does require annotation (default is to assume creator to be delegating)

[lpandzic]

Nice, so after the release the tests should pass.

[lpandzic]

I've tried it out locally and tests pass with jackson-databind 2.6.0-SNAPSHOT!
After release README.md should be updated to reflect those changes - min. dependency and removal of @JsonCreator in the example.

[lpandzic]

This issue is solved so I'm closing it.
Maybe somewhere in the future we can come up with some smarter exact algorithm for cases of multiple visible constructors.

[cowtowncoder]

Agreed.

[lpandzic]

Is release planned soon?

[cowtowncoder]

No immediate plans, but I do hope to start release planning once JsonParser-filtering is implemented for streaming API. The other bigger thing (protobuf dataformat) is complete.
We may be able to start Release Candidate process before end of April.

[lpandzic]

Does this latest release contain this feature? (jackson-databind)

[cowtowncoder]

2.6.0 has not yet been released, last one was 2.5.3, so not yet.